RESEARCH PLAN Aims: To assess the separate and interactive effects of illness severity, job characteristics, psychosocial and other factors on asthma disability. Significance: Disability in asthma is common and costly; little is known about its causes. It is likely that illness severity alone will not adequately predict disability. Other factors such as job flexibility, social supports, and smoking may also predict disability. The proposed study addresses a major research gap by investigating interrelationships among severity and co-factors in asthma disability. Design: Random sample of pulmonary and allergy internist specialists in Northern CA to enroll persons with asthma by maintaining patient visit logs. Log-in of 615 and interview of 560 by trained survey worker to assess severity of disease using a previously validated severity-of- asthma scale based on symptoms, medications, and history. Interview also uses established survey instruments to assess psychosocial variables, smoking exposure and work history. 336 subjects working at the time of baseline will be re-studied at 18 month follow-up interviews over the study. Analysis: Cross-Sectional Study. With data from the baseline survey, logistic regression to estimate the separate and combined impact of illness severity and other variables on work disability. Longitudinal study. Cox proportional hazards model to estimate the time until work disability as a function of the same risk factors; linear or logistic regression to model lost work days or disability incidence. Anticipated Results: Based on pilot and preliminary data, the proposed study will provide statistically powerful estimates of the separate and combined risk impact of severity-of asthma and other factors on disability among persons with asthma.